串列静电加速器的循环气体剥离技术

循环气体剥离是国际上普遍采地串列静电加速器改进的一项技术,介绍了该技术的原理、具体技术、现状及其发展动态。     

100 MeV紧凑型回旋加速器中洛伦兹剥离引起的束流损失

TRIUMF的加速器设施ISAC成功地展示了基于ISOL方法的放射性核束装置的驱动加速器,强流H回旋加速器是一个非常合理的选择。因此,中国原子能科学研究院根据自身的技术特点和国防核技术需求背景分析,建议研制一台75～100 MeV、200～500μA H~-回旋加速器做为驱动加速器,建设北京串列加速器升级工程,这将是一个由多台加速器灵活组合而成的、包括放射性核束靶站的多用途核科学研究设施。     

100MeV回旋加速器中心区实验台架的调试

100MeV回旋加速器中心区实验台架工作在2007年取得了重要进展。所有设备已安装、调试完毕，通过分系统和联机调试，从离子源到注入偏转板出口的束流传输效率达到了75％，内靶已出束，取得了初步的实验成果。此实验台架的建成为100MeV强流回旋加速器的磁场、高频、注入、引出、中心区、控制、束流测量等系统的结构设计及束流动力学的验证提供了一个完整的实验平台。中心区实验台架装置示于图1。     

EN串列静电加速器的维护运行

介绍了北京大学EN串列静电加速器近两年来的维护运行情况.包括加速器工作在较高端电压时的稳定运行条件,其中分压电阻阻值的稳定性及绝缘可靠性和绝缘气体的干燥程度是影响加速器在较高的端电压下稳定运行的非常重要的两个因素;气体剥离压缩循环系统对束流电荷态分布及束流传输的影响,它的使用使得中、高电荷态的离子束成倍增加,提高了束流的传输效率.另外,对小流强离子束进行积分测量的实验研究表明,PIN半导体探测器可用于流强小于0.01 nA的离子束的测量.     

13 100MeV回旋加速器剥离引出系统研制

100MeV回旋加速器加速H^-离子，要求引出束流能量为75～100MeV、束流强度为200μA的质子束流，因此决定采用剥离引出。本工作依据100MeV主磁场数据和平衡轨道数据，通过理论研究，计算100MeV回旋加速器不同能量束流引出剥离点的位置；着重计算分析70～100MeV能量的束流剥离引出的光学特性；通过理论计算确定剥离膜各项参数；完成剥离靶及其伺服驱动装置的设计；对真空系统、控制系统等相关专业提出明确的工艺流程和技术要求。最终确定100MeV强流质子回旋加速器双向引出系统初步设计。     

串列升级工程ISOL的放射性气体收集系统的设计

中国原子能科学研究院的串列加速器升级工程将利用新建的1台100MeV回旋加速器作为驱动加速器，通过新建的在线同位素分离器，在线产生要求的放射性核束，将其注入HI-13串列加速器中加速后进行各种物理实验研究。ISOL工作时，靶源系统会产生很多放射性核素，     

IREB在低压中性气体中传输的电荷中和过程的计算机模拟

文章采用蒙特卡洛方法对IREB在低压中性气体漂移管中传输初始阶段电荷中和过程进行模拟计算,对其物理过程考虑较为全面,计算与实验结果符合较好,证实IREB在低压中性气体中传输的初始阶段、电荷中和过程中,离子的碰撞电离起重要作用,而二次电子作用不显著。     

辐照加速器束流测量系统的研制

电子辐照加速器主要用于对物品的消毒灭菌、材料改性、食品保鲜等,不同能量、不同功率的电子柬流对辐照效果有较大影响。扫描盒出口处,扫描成电子帘的束流大小和扫描宽度,对辐照物品有直接的关系,因此,电子帘的测量在加速器应用中十分重要。     

串列加速器升级工程的计算机控制系统方案设计

描述了中国原子能科学研究院计划建设的串列加速器升级工程的特点,各主要设备的平面布置,以及对控制系统的基本要求,在此基础上完成了控制系统的方案设计,并建立软、硬件的实验平台,对部分设备开展了预先研究工作。     

可剥离膜的研制和去污实验验证

文章涉及自行研制的可剥离涂料在实验室和现场工程应用中的去污效率。由测试、实验和应用的结果可知，这种在基本配方中加人了纳米碳酸钙的可剥离涂料对大部分表面松散型浮尘类污染(实际遇到的大都是类似污染源)的去污效率为80％～90％．且各项指标能够满足施工需要。     

Enhanced beam quality for proton microprobes using ultrathin stripper foils in tandem accelerators

Ultrathin carbon foils (0.5 μ/cm².+) have been used as stripper foils in a tandem accelerator. The spread in the ion beam caused by scattering in ultrathin foils has been compared with the spread due to thicker carbon foils and a gas stripper. A proton beam was used at a terminal voltage of 1.3 MV. The results show a significantly smaller beam spread due to the thinnest foils, even compared with the gas stripping. The smaller beam spread and the more stable terminal voltage compared with gas stripping make the ultrathin carbon foil strippers preferable, especially for proton microprobe applications.     

A new mini gas ionization chamber for IBA applications

Novel prototypes of high resolution gas ionization chambers (GIC) were designed with increased compactness and simplicity of the setup. They have no Frisch-grid and a simple anode wire. Under certain operating conditions these mini detectors have an energy resolution comparable with that of state-of-the-art GICs of much higher complexity. They can be operated both under vacuum and atmospheric pressure. First measurements were made with protons in the energy range of 0.3-1.0 MeV. For protons at 0.3 MeV an energy resolution of about 12 keV was achieved. With a 72 MeV ¹²⁹Xe beam a relative resolution of 1.4% was obtained. Due to their versatility and reduced size the detectors can easily be applied in the field of ion beam analysis (IBA) and accelerator mass spectrometry (AMS). Since they are almost completely insensitive to radiation damage they are especially suited for use in high fluence applications such as scanning transmission ion microscopy (STIM). A comparison of the radiation hardness of the mini GIC with a Si PIN diode was therefore performed. The GIC showed no peak shift or change in energy resolution at all after collecting 10¹⁵ protons per cm² while the performance of the Si detector clearly started to degrade at 10¹² particles per cm².     

A new AMS beam line at the Erlangen tandem accelerator facility

An accelerator mass spectrometry beam line is presently being built up at the EN tandem accelerator in Erlangen. A new Cs sputter ion source is being developed, and mass separators on both the low- and high-energy sides of the tandem and an electrostatic sector field for charge-state selection have been installed. Optimization of the beam quality will be possible with a new emittance measuring device. The tandem is stabilized via a position-sensitive Faraday cup, which simultaneously measures the current of the abundant isotopes. The spectra of the rare-isotope ions are taken by differential energy loss measurements in a gas ionization chamber.     

一种新的砂岩铀矿成矿类型-- 构造-油气型

阐述了一个新的铀成矿类型——构造-油气型;讨论了该类型砂岩铀矿床形成的区域背景、构造特点、成矿环境、矿化特征和矿床成因;认为与传统的层问氧化带型砂岩铀矿床不同;强调贯通型断裂构造和油气对铀成矿所起的重要作用,对今后砂岩型铀矿普查勘探有一定的参考价值。     

串列加速器微机控制自动能量扫描系统的研制及初步调试

利用微机和单片机构成分布式控制系统参与对加速器的控制,实现了加速器在一定范围内等间隔能量点的自动调节。动态显示和稳定机器工作状态,采集并保存实验数据作为日后实验运行参数的查询和调用。     

Requirements for D-D tandem mirror reactors

Requirements for D-D barrier tandem mirror reactors are calculated from an equilibrium power balance model. To obtain adequate plasmaQ and reasonable power density, axisymmetric configurations are required to decrease barrier length and radial transport and to increase central cell beta. We find that for a reactor producing 900 MW net electric power from aQ=6.5 plasma, a central cell length of 225 m, maximumB of 15 T, and neutral beam injection energy of 700 keV are necessary. In addition to high central cell beta (70%), high barrier beta (40%) is needed to allow the ECRH power required to reduce the barrier potential. Using too much barrier ECRH power results in a decrease inQ. Nuclear elastic scattering of fusion products plays an important role in the overall plasma power balance. When nuclear scattering and coulomb scattering are included, the plasmaQ value is increased by more than 40% compared to the case when coulomb scattering alone is considered.     

A new method to estimate heat source parameters in gas metal arc welding simulation process

Heat source parameters were usually recommended by experience in welding simulation process, which induced error in simulation results (e.g. temperature distribution and residual stress). In this paper, a new method was developed to accurately estimate heat source parameters in welding simulation. In order to reduce the simulation complexity, a sensitivity analysis of heat source parameters was carried out. The relationships between heat source parameters and welding pool characteristics (fusion width (W), penetration depth (D) and peak temperature (T_p)) were obtained with both the multiple regression analysis (MRA) and the partial least-squares regression analysis (PLSRA). Different regression models were employed in each regression method. Comparisons of both methods were performed. A welding experiment was carried out to verify the method. The results showed that both the MRA and the PLSRA were feasible and accurate for prediction of heat source parameters in welding simulation. However, the PLSRA was recommended for its advantages of requiring less simulation data.